Introducing an additive to a stream of water may be necessary or desirable for fire fighting; pressure washing; spraying pesticides, fungicides, or antibiotics; spray application of fertilizers; abrasive water jet cutting; and spraying food in fish farming. It may also be important to introduce an additive to a stream of a liquid other than water. The stream of water or other liquid may be pressurized or of relatively high velocity.
In fighting certain types of fires, there is often a need to add a fire retardant or a detergent or surfactant to the stream of water used to quench the fire. Because of its high surface tension, water tends to form droplets that slide off of burning fuels such as oils. Surfactants added to the water reduce the surface tension, thereby increasing the surface area of the water droplets in contact with the substance undergoing combustion, and decreasing the time needed to quench the flames.
There are many disadvantages and limitations associated with current devices and techniques used to add a liquid to a water stream. For example, currently available devices for mixing an additive into a stream of water may rely on the Bernoulli principle. The additive is drawn up from a container into the stream of water by a partial vacuum created by the flowing stream of water. The rate at which the additive enters the stream of water is difficult, if not impossible to control when the additive is drawn up solely by the vacuum. Further, such a system provides inadequate, non-uniform mixing of the additive with the water stream.
Another device may utilize an electrically powered pump to pump the additive up from a container and into the stream of water. Use of a separate, electrically powered pump is cumbersome for use in the field or at the site of a fire. Such a pump requires an electrical power source, that may not be readily available, or that could be dangerous to use in the presence of flammable liquids.
In the case of a water tank fire truck, a detergent is sometimes simply poured into the tank of water. This system provides inadequate, non-uniform mixing of the additive with the water in the tank, and little or no control over the concentration of additive in the water stream.
In any of the current methods described above, sufficient dispersal or mixing of the additive is often inadequate for the particular use. Thus, a need exists for a more effective means and apparatus to controllably introduce an additive to a stream of a liquid and to mix the additive adequately with the stream of liquid.
In the case of fire fighting, the uniform addition and mixing of a surfactant with the water stream exiting the water hose would allow the water to be used more efficiently, thereby reducing the time needed to quench the fire, and reducing the amount of water needed to quench the fire. By reducing the time required to put out a blaze, the improvements disclosed herein are likely to also lessen the exposure to heat, toxic products of combustion, and other dangers that fire fighters face, and to reduce the damage to property caused by fire and water.